Should allow colon in metadata keys for HTTP/2 pseudo headers?

[mng12689]

Hello,

I am trying to set a metadata key/value pair for an http/2 header like so:

var meta = new grpc.Metadata();
meta.add(':authority', 'account');

This fails with the following error:

Error: Metadata key":authority" contains illegal characters
web_1              |     at normalizeKey (/app/node_modules/grpc/src/node/src/metadata.js:67:11)
web_1              |     at Metadata.add (/app/node_modules/grpc/src/node/src/metadata.js:108:9)
web_1              |     at Promise (/app/src/functions/index.js:54:10)
web_1              |     at Object.createUserSession (/app/src/functions/index.js:52:10)
web_1              |     at createUserSession (/app/src/routes/index.js:8:23)
web_1              |     at Promise.resolve.then (/app/src/lib/promisify-grpc.js:6:16)
web_1              |     at process._tickDomainCallback (internal/process/next_tick.js:135:7)
web_1              | Processing [/auth.Authenticator/CreateUserSession]

The problem is that Metadata.add() does not allow a key value pair with a key that contains a colon. However, shouldn't this be allowed considering the HTTP/2 spec specifies that pseudo headers (such as :authority) are supposed to be implemented with a leading colon?

Link to offending code:
https://github.com/grpc/grpc-node/blob/master/packages/grpc-js-core/src/metadata.ts

P.S. I did find this issue, which identifies the same problem, but does not actually discuss whether or not metadata keys SHOULD support a colon: grpc/grpc-go#613

P.P.S. Just to provide some context, I want to use the :authority header because Envoy proxy relies on this header to determine where a request should be forwarded to. Though this has little to do with gRPC, thought it might be useful to provide a legitimate use case. https://www.envoyproxy.io/docs/envoy/latest/intro/deployment_types/service_to_service.html#service-to-service-egress-listener

[mng12689]

I also just realized that gRPC metadata is not the same thing as HTTP/2 headers (and I'm guessing aren't implemented as such), in which case this issue is probably not relevant. Is there a way to modify the underlying HTTP/2 headers for a gRPC request?

[murgatroid99]

You can't directly set the :authority header because gRPC internally handles HTTP2 protocol pseudo-headers. You can modify the authority for an entire client by setting the option "grpc.default_authority" at client construction, and I think you can set it for a single call by passing it in the host key in the options call argument.

gRPC metadata does in fact correspond directly to HTTP2 headers.

[imseon]

@murgatroid99 It works fine! Thanks